The present invention relates to a drive system for a motor vehicle, and more particularly to a drive system including an engine followed by a continuously variable transmission.
U.S. Pat. No. 4,735,113 issued to Yamamuro et al., on Apr. 5, 1988 discloses a drive system for a motor vehicle. This known drive system includes an engine followed by a continuously variable transmission. In such drive system, a control for the engine is independent from a control for the continuously variable transmission. In the event an accelerator pedal is released from a depressed position, a torque generated by the engine drops at a predetermined rate with respect to time regardless of a shift position which a manual valve of the continuously variable transmission is placed at. The manual valve has a plurality of shift positions including a normal forward drive position, namely D range position, and an engine braking forward drive position, namely L range position. If the setting is such that after the accelerator pedal has been released, the torque generated by the engine drops at a gradual rate to provide a good ride feel for operation with the manual valve placed at the D range position, an engine braking is insufficient after the accelerator pedal has been released with the manual valve placed at the L range position. On the other hand, if the torque generated by the engine drops at an increased rate with respect time with the manual valve placed at the D range position, the engine torque drops quicker than the continuously variable transmission shifts down. This induces a shock.
An object of the present invention is to improve a drive system for a motor vehicle including an engine followed by a continuously variable transmission such that after a power demand has disappeared, a torque generated by the engine drops in such a manner as to provide a good ride feel during operation of the continuously variable with a manual valve placed at normal forward drive range position and a sufficient engine braking during operation of the continuously variable transmission with the manual valve placed at engine braking forward drive position.